Ring size discrepancies in different materials

Discussion in 'General Discussion' started by Tigermoth, Feb 27, 2013.

  1. Tigermoth
    Tigermoth New Member
    Hi all just wondering if anyone else has had any size discrepancies in using different materials.

    For example I ordered 2 rings, both from the same file 1 FUD and 1 Stainless. But on arrival the FUD shows X but the Stainless is a W.
    So I tried another ring, test prints in WSF proved to be the same size as I had made on the file...but the Sterling print came back 2 SIZES smaller!

    Effectively it seems I now have to order each model in each size and material to truly know what size it will be...that is, if it prints the same every time? At any rate...I'm not in a position to afford this right now :/

    So I'm assuming its shrinkage in the casting process, but I thought I read somewhere this was taken into account and offset?

    I know there's a lot of ring makers on here, would be good to hear how they manage this issue, particularly if they are being purchased by customers as one size and its being delivered as a completely different size
  2. UniverseBecoming
    UniverseBecoming Well-Known Member
    Was it in Collada file format? If so, the problem is being corrected, see here.
  3. Tigermoth
    Tigermoth New Member
    No, .stl.
    I think this is perhaps unrelated.
    All my WSF/FUD rings seem to come out accurate to my scale used in construction, just as soon as I get the same files done in Sterling or Stainless the inside diameters differ.
  4. stannum
    stannum Well-Known Member
    Check the accuracy in the material pages. Some materials are very "random" with no way to get exact prints, while others should be better and then you got a dud. Steel is +-2mm and silver +-0.125mm.
  5. Tigermoth
    Tigermoth New Member
    So you're saying that the the sizes are inconsistent, even when using the same file and material? If so. that's worse than I thought.
    1-2mm is quite a discrepancy when it comes to ring sizes, that would explain the Stainless...but why is the Sterling so out? 2 ring sizes is a fair bit more than the 0.125mm stated. :confused
  6. Youknowwho4eva
    Youknowwho4eva Shapeways Employee Community Team
    Have you emailed service about the shrinkage of your silver ring? Stainless shrinkage is usually from the infusion process, which heats the metal, allowing gravity to take over. So it's harder to control.
  7. Tigermoth
    Tigermoth New Member
    Not yet...just wanted to see if this was a common issue first.
    If the discrepancies are consistent then its not so bad as I will adjust sizes for the material, if not, then its a lot of moving goal-posts all of a sudden :/
  8. Youknowwho4eva
    Youknowwho4eva Shapeways Employee Community Team
    Email service, and they will tell if exactly if it's to be expected or not. Stainless is the only material I'd expect major shifts of up to 2mm, and even then I haven't seen that big of a shift on my own items.
  9. AlanHudson
    AlanHudson Shapeways Employee Dev Team
    My read of the accuracy between WSF and Silver says there would be .307mm possible difference between a ring size 12. This is .15mm WSF accuracy + .15% * 21.39 + .125mm accuracy of silver. So a size 12 ring could become 11.5 ish. or if it breaks the other way it could be 12.5

    I'm doing a fair bit of ring printing right now so I'll try some WSF version of the silver process and see how close they are and report back. Likely will take about a month to collect data. I also suspect polishing will have some affect as well. Not sure I've got the budget to do all the variations but I'll report what I do.
  10. Tigermoth
    Tigermoth New Member
    Thanks for that, be interested to see your results.
    I will ask and see what they say.
    Its been pretty disappointing as much of my latest orders, although printed well, came into size differences...not just rings, but bezel settings for stones were undersized too :(

    What I would really like to know is if these discrepancies are CONSISTENT...then I could offset the original file until I get it right. A few fractions of a mm might not seem much to some, but if you are trying to sell these to people as specific sizes, then 2 sizes out may not be acceptable to some?

    Last edited: Mar 18, 2013